Windheim, M, Höning, S, Leppard, KN et al. (4 more authors) (2016) Sorting motifs in the cytoplasmic tail of the immunomodulatory E3/49K protein of species D adenoviruses modulate cell surface expression and ectodomain shedding. Journal of Biological Chemistry, 291 (13). pp. 6796-6812. ISSN 0021-9258
Abstract
The E3 transcription unit of human species C adenoviruses (Ads) encodes immunomodulatory proteins that mediate direct protection of infected cells. Recently, we described a novel immunomodulatory function for E3/49K, an E3 protein uniquely expressed by species D Ads. E3/49K of Ad19a/Ad64, a serotype that causes epidemic keratokonjunctivitis, is synthesized as a highly glycosylated type I transmembrane protein that is subsequently cleaved resulting in secretion of its large ectodomain (sec49K). Sec49K binds to CD45 on leukocytes, impairing activation and functions of NK cells and T cells. E3/49K is localized in the Golgi/trans-Golgi-network (TGN), early endosomes and on the plasma membrane, yet the cellular compartment where E3/49K is cleaved and the protease involved remained elusive. Here we show that TGN-localized E3/49K comprises both newly-synthesized and recycled molecules. Full-length E3/49K was not detected in late endosomes/lysosomes but the C-terminal fragment accumulated in this compartment at late times of infection. Inhibitor studies showed that cleavage occurs in a post-TGN compartment and that lysosomotropic agents enhance secretion. Interestingly, the cytoplasmic tail of E3/49K contains two potential sorting motifs, YxxΦ and LL that are important for binding the clathrin adaptor proteins AP-1 and AP-2 in vitro. Surprisingly, mutating the LL motif, either alone or together with YxxΦ, did not prevent proteolytic processing, but increased cell surface expression and secretion. Upon Brefeldin-A treatment cell surface expression was rapidly lost, even for mutants lacking all known endocytosis motifs. Together with immunofluorescence data, we propose a model for intracellular E3/49K transport whereby cleavage takes place on the cell surface by matrix-metalloproteases.
Metadata
Item Type: | Article |
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Authors/Creators: |
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Copyright, Publisher and Additional Information: | © 2016, The American Society for Biochemistry and Molecular Biology. This is an author produced version of a paper accepted for publication in Journal of Biological Chemistry. Uploaded in accordance with the publisher's self-archiving policy. |
Keywords: | Adenovirus; Intracellular trafficking; Protein sorting; Shedding; Viral immunology; Adenovirus E3 proteins; CD45; E3/49K; Epidemic Keratoconjunctivitis; Immune evasion |
Dates: |
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Institution: | The University of Leeds |
Academic Units: | The University of Leeds > Faculty of Biological Sciences (Leeds) |
Depositing User: | Symplectic Publications |
Date Deposited: | 22 Mar 2016 14:11 |
Last Modified: | 19 Jan 2018 17:33 |
Published Version: | http://dx.doi.org/10.1074/jbc.M115.684787 |
Status: | Published |
Publisher: | American Society for Biochemistry and Molecular Biology |
Identification Number: | 10.1074/jbc.M115.684787 |
Related URLs: | |
Open Archives Initiative ID (OAI ID): | oai:eprints.whiterose.ac.uk:96530 |